1. Field of the Invention
The present invention is generally directed to coated abrasive products, and in particular coated abrasive products and processes for forming same that employ a binder formulation having multiple pathways for curing.
2. Description of the Related Art
Coated abrasive products fundamentally include a substrate or backing member that serves as a dimensionally stable component, on which an abrasive-containing layer is deposited. In traditional coated abrasives, abrasive grains of the abrasive layer are adhered to the backing member through use of a maker coat, which is an adhesive binder composition for anchoring the as-deposited abrasive grains. Most typically, processing continues with deposition of a size coat that lends structural integrity to the abrasive layer. In the context of traditional coated abrasives, the abrasive grains are generally randomly oriented and form a fairly uniform layer.
Engineered or structured abrasives have been developed to provide improved performance over traditional coated abrasive products. Structured abrasives also generally utilize a backing member, but the abrasive layer is deposited in order to form a pre-configured pattern. Such structured abrasives generally exhibit enhanced grinding characteristics over conventional abrasive products, such as providing sustained cut rate, consistent surface finish, and extended life.
In the context of both traditional coated abrasives and structured abrasives, thermal curable binders have been used to adhere the abrasive layer to the backing member or substrate, as well as to stabilize the abrasive grains. However, thermal curing suffers from numerous drawbacks including, often times, extended cure times resulting in unwanted shifting of abrasive grain position. Particularly in the context of structured abrasives, the pattern of grains may be disrupted during rheological changes of the binder formulation during heating and/or during handling of the structured abrasive prior to or during heat treatment.
In an effort to address such disadvantages, so-called radiation-curable binder systems have been developed, which advantageously permit short curing cycles. Such radiation curable binders include UV-curable binders as well as e-beam curable binders. However, radiation curable binders are not without their drawbacks as well. For example, particularly in the case of silicon carbide-based abrasives, the depth of penetration of the radiation is limited. Further, dyes present within the binder formulation can cause issues with radiation penetration as well, resulting in incomplete curing.
In an effort to address the processing and performance characteristics associated with known coated abrasives, and in particular structured abrasives, U.S. Pat. Nos. 5,863,306 and 5,833,724 describe various coated abrasives formed utilizing a binder formulation that combines radiation curable and thermally curable components. During processing, viscosity is modified through use a functional powder that is added to a coated intermediate product prior to curing. The functional powder is intended to adjust a viscosity of the intermediate product, to retain structural integrity during processing such that its engineered shape is maintained prior to and during curing.
Despite advances provided in the art, as exemplified in the '306 and '724 patents for example, a need continues to exist for superior coated abrasives and methods for forming same, and which further lend themselves to large-scale manufacturing operations.